Afterburner control for dual injector turbine pump



p 1962 M. F. ALEXANDER 3,052,089

AFTERBURNER CONTROL FOR DUAL INJECTOR TURBINE PUMP Filed March 21, 19584 Sheets-$heet 1 .EZEZZZQZ" Sept. 4, 1962 M. F. ALEXANDER AFTERBURNERCONTROL FOR DUAL INJECTOR TURBINE PUMP Filed March 21, 1958 4Sheets-Sheet 2 EEZZZQF Sept. 1962 M. F. ALEXANDER 3,052,089

AFTERBURNER CONTROL FOR DUAL INJECTOR TURBINE PUMP Filed March 21, 19584 Sheets-Sheet 3 Sept. 4, 1962 M. F. ALEXANDER AFTERBURNER CONTROL FORDUAL INJECTOR TURBINE PUMP Filed March 21, 1958 4 Sheets-Sheet 4 a J o J0 ru 0 M M m w w w 4 w w W Z a 3 3 4 -kih 4 1 T 8 27\ 4 W M o w 4 w 4mm. a M 4 4/ 4 4 a (U 0 no 0 My w w w w m w w m United States PatentOfilice 3,952,089 Patented Sept. 4, 1962 3,952,039 AFTERBURNER @QNTROLFUR DUAL INJECTOR TURBINE PUMP Melville F. Alexander, Euclid, Ohio,assignor to Thompson Rama Wooldridge, Inc, a corporation of Ohio FiledMar. 21, 1958, Ser. No. 723,027 2 Claims. (Cl. 60-356) This inventionrelates to a fluid flow control system, and particularly to anafterburner fuel control system for a turbojet aircraft engine. Theillustrated embodiment of the invention comprises an air turbine pumpand a control unit for controlling supply of fuel from the pump to adual injection system in the tail cone of a turbojet engine.

It is an object of the present invention to provide an afterburner fuelcontrol system which enables the pilot to shift from single to dualinjection operation without danger of flooding or explosion.

It is a further object of the present invention to provide a controlsystem for supplying fuel to a pair of fuel discharge devices and forcausing the total of the flow rate to said devices to vary as a smoothfunction of an input variable over a region of transition from fuelsupply to one device to fuel supply to both devices.

Another object of the invention resides in the provision of anafterburner fuel control system for varying the fuel supply rate in apredetermined manner as a function of compressor discharge pressure.

Still another object of the invention resides in the provision of anovel and improved afterburner fuel supply system and particularly inthe provision of such a system wherein a single valve assembly isadapted to vary the supply of fuel to a dual injection system in apredetermined manner.

A further object resides in the provision of an afterburner fuel supplysystem having means for initating flow to a second fuel discharge deviceof :a dual fuel injection system simultaneously with movement of a fuelflow controlling valve member into a predetermined position.

Yet another object of the invention is to provide a novel and improvedassembly comprising an air turbine driven fuel pump and a control unitfor controlling supply of fuel from the pump to the afterburner of aturbojet engine.

Other objects, features and advantages of the present invention will beapparent from the following detailed description taken in connectionwith the accompanying drawings, in which:

FIGURE 1 is a diagrammatic illustration of a turbojet engine embodyingan afterburner fuel control system in accordance with the principles andteachings of the present invention;

FIGURE 2 is a diagrammatic perspective view of an air turbine drivenafterburner pump and fuel control assembly in accordance with thepresent invention;

FIGURE 3 is a further diagrammatic perspective view of the assembly ofFIGURE 2;

FIGURE 4 is a somewhat diagrammatic longitudinal sectional view of thefuel control unit of FIGURE 2;

FIGURE 5 is a graph illustrating certain characteristics of a. fuelcontrol system embodying the teachings of the present invention;

FIGURE 6 is a graph illustrating further character istics of a fuelcontrol system in accordance with the present invention; and

FIGURE 7 is a simplified diagrammatic view illustrating the manner ofoperation of the fuel metering valve of the fuel control unit of FIGURE4.

As shown on the drawings:

Referring to FIGURE 1, a turbojet aircraft engine is I indicatedgenerally at 10 and includes a compressor section 11 supplying air to acombustion chamber indicated at 12. A turbine 14 is mounted on a commonshaft 15 with the compressor section 11 and is driven by the products ofcombustion emanating from the combustion chamber 12 to drive thecompressor section.

The engine is provided with a further combustion region indicatedgenerally at 18 in the tail cone section 19 of the engine which issupplied with fuel by means of a dual injection system indicatedgenerally at 20. The dual injection system may comprise an inner burnerring or core 22 and an outer burner ring or annulus 23, each of which isdesigned to discharge an annular stream of fuel into the combustionregion 18.

Means is provided for controlling the supply of fuel to the dualinjection system 20 comprisng a unitary assembly or package 30 includingan air turbine driven fuel pump unit 31, FIGURES 2 and 3, and a fuelsupply control unit 32. The fuel impeller section 35 of pump 31 isdriven by means of an air turbine section 36 having a turbine mounted ona common shaft with the fuel impeller means. Fuel is supplied from afuel tank to inlet 40 of the fuel impeller section and is delivered fromthe impeller section by means of a conduit indicated at 41 in FIGURE 2connecting with fuel control unit 32. The turbine section 36 of pump 31is supplied with air from compressor section 11 by means of a conduitindicated at 44 in FIGURE 1 connecting with an air inlet 45 of controlunit 32. The air inlet 45 communicates with an air outlet 46, FIGURE 2,under the control of the unit 32, and the air outlet 46 connects withthe turbine section 36 of the pump by means of a conduit indicated at 48in FIGURE 2. The air supply from compressor section 11 via conduit 44thus serves to drive the turbine section of the pump 31 to supply fuelunder pressure to the control unit 32 via fuel conduit 41. The controlunit 32 controls the supply of air to the turbine section of the pump tocontrol the speed and hence the fuel discharge pressure of the pump.

The control unit 32 is suitably referenced to compressor dischargepressure by means of a line 52, and the fuel control unit is operativeto vary fuel supply to the afterburner section of the engine as apredetermined function of compressor discharge pressure as willhereinafter be described in detail. The control unit 32 serves tocontrol the delivery of fuel from fuel conduit 41 to core port 54 andannulus port 55 which are connected by means of conduits 57 and 58 withcore burner secton 22 and annulus burner section 23 of the engine 10.The assembly 30 is designed to be controlled by means of a manual fuelflow demand lever which is suitably coupled with an input control shaft76 of fuel control unit 32.

FIGURE 4 illustrates a preferred embodiment of the control unit 32 ofFIGURES 1 to 3 and comprises a fuel inlet port 80 which connects withthe fuel conduit 41 of FIGURE 2. Fuel flows from inlet 80 to ports 82and 83 of a valve member 84 which is rotatably and axially slidablymounted relative to a sleeve 86 having peripheral slots -87 and 88therein leading to respective annular chambers 9t) and 91. The chambers90 and 91 connect with the core and annulus ports 54 and 55 shown inFIGURE 3 for delivering fuel to the core and annulus burners 22 and 23of FIGURE 1 via passages 94, and 95, 96 and 97, respectively. Thepassage 94 communicates directly with the core port 54 and the passage97 communicates directly with the annulus port 55. The valve body 84 isconnected by means of spider portions 84a with a central shaft 100 whichhas an enlarged splined end portion 100a axially shiftable relative to asplined bore 76-12 of shaft 76. The splines key the shaft 100 forrotation with the shaft 76 while allowing axial movement of the shaft100 aoeaosa relative to the shaft 76. As shaft 76 is rotated from aninitial position in response to movement of a pilot operated manual fuelflow demand lever, valve body 84 is rotated and port 82 of the valvebody registers with a progressively increasing area of the slot 87 insleeve 86 to tend to deliver more fuel to the core burner 22.

Fuel supply passage 94 is referenced to a chamber 103 defined by adiaphragm 105 and an axially expansible and contractable bellows 107 bymeans of passages 109 and 110. Inlet 80 is referenced to a secondchamber 112 defined by diaphragm 105 and a similar bellows 113 by meansof a passage 115. Thus, as valve body 84 is rotated to increase the areaof registration between port 82 and slot 87 in sleeve 86, the pressurein annular chamber 90 will tend to increase relative to the fuelpressure at inlet 80 to tend to cause diaphragm assembly 120 betweenchambers 3 and 112 to move to the left. Spring 121 acting on lever 122causes lever 122 to tend to rotate about its pivot 124 in acounterclockwise direction to follow movement of end 120a of diaphragmassembly 120. End 1220 of lever 122 thus tends to move closer todischarge orifice 125 and further away from discharge orifice 126. Thistends to increase the pressure in air valve control chamber 130 anddecrease the pressure in control chamber 131 causing piston assembly 133to move to the right and causing air valve member 135 to uncover more ofthe inlet 46 to the air driven turbine section 36. Air from thecompressor enters inlet 45 as indicated in FIGURE 1 and is deliveredinto chamber 140, FIGURE 4, from which it travels past edge 135a of airvalve 135 and enters air outlet 46 for delivery by conduit 48, FIGURE 2,to the turbine section 36. The chamber 140 communicates with air controlchambers 130 and 131 by means of passages 143, 144 and 145, and 143, 146and 147, respectively, under the control of adjustable valve members 150and 151. The chambers 130 and 131 communicate with discharge orifices125 and 126 via passages 145 and 1 53, and 154, respectively, and airdownstream of orifices 125 and 126 escapes from the control unit via apassage 156.

Thus, when shaft 76 is rotated to demand more fuel, diaphragm assembly120 causes air valve member 135 to supply more air to the turbinesection 36 to increase the discharge pressure of the pump section 35,until the pressure in chamber 112 referenced to the fuel inlet 80reaches a predetermined value in relation to the pressure in coreannular chamber 90. The value of the pressure differential which ismaintained between chambers 112 and 103 is determined by means of a setscrew 160 which has an end portion 160a for varying the compression ofspring 121. The screw 160 thus serves to control the pressure dropacross the metering orifice defined by the registering portions of port82 and slot 87 For closing air valve 135 in a predetermined angularposition of shaft 76, the shaft 76 is provided with a earn 164 securedto the shaft by means of a nut 165 to be rotatable therewith and havingan eccentric portion indicated at 164a for normally maintaining a pin168 in the raised position shown in FIGURE 4 relative to end 122b oflever 122 against the action of a spring 169. When the shaft 76- is inits inital angular position closing the metering orifices defined byports 82 and 83 and slots 87 and 88, cam portion 164a is out of registrywith pin 168, so that spring 169 maintains pin 168 in a depressedcondition where end 168a of pin 168 maintains lever 122 in an extremeclockwise position closing discharge orifice 126 and thus maintaining ahigh pressure in air control chamber 131 to maintain valve 135 in closedposition. As soon as shaft 76 is rotated to demand fuel, cam section164a engages pin 168 to raise the same to the position shown allowingcomplete freedom of movement of lever 122 between discharge orifices 125and 126.

Shaft 180 of diaphragm assembly 120 extends within annular bellows 113and is connected with a diaphragm assembly 181 by means of a collar 183and nut 184. The

1.2. collar 183 is fixed with respect to shaft 180 so that the diaphragmassembly 181 is rigidly coupled with diaphragm assembly 120. Thediaphragm assembly 181 is interposed between a pair of chambers 200 and201. Chamber 200 is referenced to turbine inlet air pressure whichexists at air outlet 46 leading to the turbine impeller section 36 ofpump 31 by means of a port 205. Chamber 200 communicates with chamber201 via passages 207 and 208 under the control of a valve member 210which is adjustable by screw means 212. Thus, under stable conditions,the pressure in chambers 200 and 201 will be equal to turbine inletpressure, and diaphragm assembly 181 will not affect operation ofdiaphragm assembly 120. If, however, the pressure in chamber 103 shouldincrease suddenly relative to the pressure in chamber 112, causing asudden opening movement of valve 135 and a consequent sudden increase inturbine inlet air pressure, this increased turbine inlet air pressurewould momentarily cause a pressure differential between chambers 200 and201 which would be equalized under the control of valve member 210 overa predetermined time period during which further movement of diaphragmassembly 120 tending to further open valve 135 would be resisted. Thesystem including diaphragm assembly 181 and chambers 200 and 201 thusconstitutes a flgedback system for stabilizing operation of the airvalve In the illustrated embodiment, fuel is not supplied to the annulusburner 23 until a predetermined angular position of shaft 76 is reached,at which position a raised cam shoulder 76c moves out of registry with avalve member 225 to allow the valve member to assume an open positionunder the urging of a spring 226. Before this angular position of shaft76 is reached, valve member 225 restricts communication between passages228 and 229 to provide a relatively low pressure in chamber 233, passage228 referencing chamber 233 to pressure in annular chamber 91 downstreamof valve 84 and upstream of annulus burner 23. A chamber 236 isreferenced to fuel inlet pressure by means of a passage 238communicating with fuel inlet Diaphragm assembly 240 IS responsive tothe differential in pressure between chambers 233 and 236, and withvalve member 225 in the flow restricting position shown in FIGURE 4,valve member 242 is held in open position relative to valve port 243 andprovides a relatively high pressure in chamber 246. Fluid flows fromchamber 246 to passage via orifice 252 so that the pressure in chamber246 is normally intermediate fuel inlet pressure and the pressure atpassage 95. With valve member 225 in full restricting posit on, arelatively high pressure exists in chamber 246 relative to the pressurein passage 95 so as to bias valve member 254 to the left against thebias of spring 257 to close valve ports such as indicated at 254abetween passages 95 and 96 to cut off the supply of fuel to the annulusburner 23. A spring 260 may be provided tendmg to urge valve member 254toward closing relation but allowing opening of ports 254a by spring 257when valve member 225 is moved to open position.

When input shaft 76 has moved to a predetermined angular position, camportion 76c moves out of registry with valve member 225 and valve member225 moves to an open position to apply pressure from chamber 91 tochamber 233 tending to move valve member 242 toward restricting relationto orifice 243 to tend to decrease the pressure in chamber 246.Reduction of pressure in chamber 246 allows valve member 254 to move tothe right tending to open ports 254a and supply fuel to the annulusburner via passages 96 and 97 and conduit 58 shown in FIGURE 1.

Screw means indicated at 270 is operative to adjust the force exerted byspring 271 against diaphragm assembly 240, so that adjustment of thisscrew means 270 adjusts the pressure drop across the annulus meteringorifice defined by the registering portions of port 83 and slot 88.

For varying the rate of flow of fuel to the afterburner in accordancewith compressor discharge pressure for a given angular position of shaft76, a chamber 300 is referenced to compressor discharge pressure bymeans of a port 303 and line 52 illustrated in FIGURE '1. The chamber300 is bounded in part by annular bellows members 305 and 306 and a cupmember 307. A vacuum chamber 309 is defined by plate 310, bellows 306and 313 and end wall 307a of member 307. Plate 310 is connected with apin 317 abutting a flapper valve 320 in chamber 321. As compressordischarge pressure increases, the pressure in chamber 300 increases totend to move plate 310 to the right, shifting pin 317 connected withplate 310 to the right to actuate flapper valve 320, which is pivotallymounted by means of a double leaf spring arrangement 322 in chamber 321.

Chamber 321 is referenced to fuel inlet 80 via a passage 330, meteringorifice 331, passage 332 and orifice 333. Fuel is bled from chamber 321through a metering orifice 236 and a passage 237 to a further passage339 connecting with the pump inlet 40 seen in FIGURES 2 and 3. Thepressure in chamber 321 is thus intermediate pump discharge and pumpinlet pressure and is referenced to a chamber 350 by means of passagessuch as indicated at 351 in a piston member 352. The pressure in chamber350 acts on one side of a piston assembly 360, while fuel pressure frompassage 339 is referenced to a chamber 362 by means of a passage 363. Acentral area 360a of piston assembly 360 is exposed to fuel dischargepressure from fuel inlet 80. It will be observed that piston assembly360 is connected with valve shaft 100 by means of a connector 362 sothat if piston 360 is shifted axially, valve body 84 will likewise shiftaxially. Slots 87 and 88 in sleeve 86 are of such a configuration thatshifting of the valve body 84 to the left will increase the area of themetering orifices leading to the core and annulus burners, for a givenangular setting of input shaft 76. As compressor discharge pressureincreases in chamber 300, plate 310 moves to the right moving pin 317against flapper valve 320 which in turn moves piston member 352 to theright against the action of a spring 370. Movement of flapper valve 320to the right tends to restrict an orifice indicated at 372 downstream ofOI'fiJlCC 333 to tend to decrease the pressure in chamber 321 andconsequently in chamber 350 and thus to cause piston assembly 360 andvalve member 84 to move to the left. Movement of piston assembly 360 tothe left compresses spring 370 to move flapper valve 320 to the leftopening orifice 372' and increasing the pressure in chambers 321 and 350until equilibrium is restored.

It will thus be understood that the valve body 84 shifts angularly inreponse to rotation of shaft 76 and shifts axially in response tochanges in compressor discharge pressure introduced at 303 so as to becapable of providing a fuel supply rate varying as a function of anangular input and as a function of compressor discharge pressure.

FIGURE 5 is illustrative of a typical performance characteristic for thecontrol unit of FIGURE 4 and represents a plot of fuel flow in poundsper hour divided by compressor discharge pressure in pounds per squareinch absolute as a function of power lever angle in degrees. It will beunderstood that the variable power lever angle refers to the pilotsmanual fuel flow demand lever angle. Angular movement of this lever istransmitted by means of a suitable remote control system to causeangular movement of input shaft 76 of the control unit shown in FIGURE4. It will be observed that the ratio of fuel flow to compressordischarge pressure is illustrated as increasing over the range wherefuel is supplied to the core burner only between power lever angles of90 and 115, after which core fuel supply is illustrated as leveling offat a ratio value of approximately 165. Above the ratio of fuel flow tocompressor discharge pressure increases at a uniform rate, while below110, the variation of the ratio with power level angle is a function ofcompressor discharge pressure in the range from 15.3 pounds per squareinch absolute to 39 pounds per square inch absolute, curve 401representing the variation for a compressor discharge pressure of 15.3pounds per square inch absolute, curve 402 illustrating the variationfor a compressor discharge pressure of 2.6 pounds per square inchabsolute and curve 403 illustrating the variation for compressordischarge pressures of 39 pounds per square inch absolute up to amaximum of 170.6 pounds per square inch absolute. It will be understoodfrom this curve that fuel flow is to increase as a function ofcompressor discharge pressure, and in the range of from 110 to forexample, fuel flow is to be a linear function of compressor dischargepressure. Such a fuel flow characteristic may be obtained by the controlunit of FIGURE 4 by arranging the metering orifices defined by the ports82 and S3 and slots 87 and 83 so as to provide a progressivelyincreasing area as the valve body 84 is shifted axially to the left withincreasing compressor discharge pressure in chamber 300 and by providinga progressively increasing area of the metering orifices as shaft 76 isrotated in the direction of the arrow 405 in FIGURE 4. It will also benoted that for compressor discharge pressures of 39 pounds per squareinch and above, fuel fiow is to be a linear function of power levelangle at a given compressor discharge pressure for angles above 100.

FIGURE 6 illustrates further characteristics of a preferred embodimentin accordance with the present invention wherein the ratio of fuel flowto compressor discharge pressure is plotted as a function of power levelangle for compressor discharge pressures in the range of 39 pounds persquare inch absolute and above. Curve 410 represents the core fuel flowWhile the curve 411 illustrates the annulus fuel flow and the dash curve412 illustrates the sum of annulus and core fuel flow for power levelangles beyond 115. It will be observed that in a system in accordancewith this illustrated embodiment, it is contemplated that at a powerlevel angle in the neighborhood of 115, core fuel flow to the coreburner (for a given compressor discharge pressure) will be sharplyreduced as fuel begins to be supplied to the annulus burner. Thisprovision prevents flooding or explosion at the time that fuel begins tobe supplied to the annulus burner. It is contemplated that the core fuelcharacteristic may be variable from the curve represented by lines403-415416 in FIGURE 5 to the curve represented by lines 410, 420 and421 in FIGURE 6, so that the fuel flow rate to compressor dischargepressure ratio will be adjustable between the limits of and for powerlevel angles in the neighborhood of 115 and above. By this means, thetotal afterburner fuel flow rate may be a substantially linear functionof power lever angle as represented by the lines 410a and 412 in FIG-URE -6.

FIG. 7 is a simplified diagrammatic view illustrating the manner inwhich the ports 82 and 83 and the slots 87 and 88 cooperate to definevariable area metering orifices controlling fuel delivery in the controlunit of FIGURE 4. As the valve body 84 is rotated in the direction ofthe arrow 405 in FIGURE 4 by means of shaft 76, ports 82 and 83 move inthe direction of the arrows 430 and 431 relative to slots 87 and 38 inFIGURE 7, while as compressor discharge pressure in chamber 300increases and valve body 84 moves axially to the left in FIGURE 4, theports 82 and 83 move in the direction of the arrows 433 and 434 inFIGURE 7. The position of the ports 82 and 83 with full compressordischarge pressure is represented by the rectangles in dash outline at436 and 437 in FIGURE 7. The position of the ports 82 and 83 in solidoutline in FIGURE 7 corresponds to a minimum compressor dischargepressure. It will be observed that for a fixed minimum compressordischarge pressure, edge 440 of port 82 will move along imaginary line441 with increasing power lever angle While edge 444 of port 83 willmove along imaginary line 445. For a minimum compressor dischargepressure, as port 82 is moved along line 441, the area of registrationbetween port 82 and slot 87 will progressively increase until leadingedge 448 of port 82 reaches point 450 along the edge of slot 87corresponding to a power lever angle somewhat less than 115. Furthermovement of port 82 along imaginary line 4411 will result in a decreasein the area of registration between port 82 and slot 87, which may bethought of as generally corresponding to the portion 420 of curve 410 inFIGURE 6. It will be understood that restricting the area ofregistration between port 82 and slot 87 will tend to reduce thepressure in annulus 90 which in turn will tend to reduce the flow offuel to the core burner for a given compressor discharge pressure.Similarly, as port 83 is moved along imaginary line 445 for a minimumcompressor discharge pressure, when valve member 225 is actuated to openports 25411, for example at a power level angle just less than 115 asindicated by curve 411 in FIGURE 6, fuel will begin to flow to theannulus through the metering orifice defined by port 83 and slot 88. Atthis point leading edge 452 of port 83 will coincide with a point in theneighborhood of that indicated at 453 along the edge of slot 8 8 toprovide a substantial area of registration between slot 8 8 and port 83and accommodate a substantial increase in annulus fuel flow as the powerlever is moved progressively in the neighborhood of 115. It will beobserved that for any given angular setting of the power lever angle ifcompressor discharge pressure increases corresponding to a movement ofthe ports 82 and 33 to the left as indicated by the arrows 433 and 434,an increased area of registration between ports 82 and 83 and slots '87and 88 will result providing an increased flow to the core and annulusburners. It will be appreciated that to vary the core fuel drop at theneighborhood of 115 as represented in FIGURE 6 at 420, the arearestriction of slot 87 rep-resented by lines 460 and 461 could bevaried, and in the limiting case, the slot edges could be represented bythe dash lines 463 and 464 with no decrease in the area of registrationbeyond point 450, this condition corresponding to the curve 403-415416in FIGURE 5.

Summary of Operation Assuming that the shaft 76 is initially in offposition, as the pilot shifts the fuel supply demand lever to onposition, cam portion 164a on shaft 76 raises pin 168 to disengageflange 1 68a from lever 122 to unlock lever 122 and allow opening of airvalve 135.

As the power lever is moved between angles of 90 and approximately 114,the area of registration between port 82 and slot 87 progressivelyincreases. The progressive increase in area of registration brings abouta tendency for pressure in annulus 90 to increase which in turn tends toincrease the pressure in chamber 103 and move diaphragm assembly 120 tothe left tending to reduct the air pressure in chamber 131 and increasethe air pressure in chamber 130 to open valve 135 and increase thesupply of air to the turbine section 36 driving fuel pump section 35Shown in FIGURES 2 and 3. This results in a pressure increase at fuelinlet 80 which is communicated to chamber 112 to balance the diaphragmassembly 120 in a new position corresponding to a new position of thevalve 135. In this manner, increasing area of registration between port82 and slot 87 results in a progressively increasing discharge pressurefrom the pump unit 35 and a progressively increasing 8 fuel flow to thecore burner indicated at 22 in FIG- URE 1.

For any given setting of the fuel supply demand lever, an increase incompressor discharge pressure which is referenced to chamber 300, shiftsvalve body 84 to the left increasing the area of registration of port 82with slot 87 and increasing the rate of flow of fuel to the core burner,generally in direct proportion to the increase in compressor dischargepressure.

When an angle of approximately 114 is reached as represented in FIGURE6, cam shoulder 76c of shaft 76 moves out of engagement with valvemember 225 to begin the supply of fuel to the annulu burner indicated at23 in FIGURE 1. Specifically, opening of valve 225 references pressurein annulus 91 to chamber 233, tending to restrict orifice 243 anddecrease pressure in chamber 246, allowing spring 257 to open ports254a.

At this same power lever angle of approximately 114, the area ofregistration between port 82 and slot 87 may begin to rapidly decreaseto cause a decrease in the area of registration corresponding to thecurve portion 420 in FIGURE 6 and causing a corresponding drop in thesupply of fuel to the core burner as the power demand lever is movedfro-m an angle of approximately 114 to an angle of approximately 116. Asillustrated in FIG- URE 6, the drop in fuel flow to the core burner mayexactly compensate for the increase in fuel flow to the annulus burneras represented by the curve 411 in FIG- URE 6, so that the sum of thecore plus annulus fuel flow constitutes a smooth function of power leverangle over the regions from to 130. In fact, as represented in FIGURE 6,the total flow is a substantially linear function of power lever anglesfor angles between and This relatively smooth transition from flow tothe core burner to flow to both the core and annulus burners preventsflooding or explosion in the afterburner section of the engine.

Adjustment of the screw means varies the bias of spring 121 on lever122, and thus regulates the pressure difierential between chambers 112and 103 which will be maintained by the system. Screw means 160 thusadjusts the pressure drop which will be maintained across the meteringorifice defined by the registration between port 82 and slot 87.

Similarly, screw means 270 provides for adjustment of the bias of spring271 to regulate the pressure drop across the metering orifice defined bythe registration of port 83 and slot 88.

It may be noted that in FIGURE 4, valve 254 would normally be closedwith valve member 225 in its flow restricting position shown in FIGURE4, but has been shown open in order to illustrate the valve ports 254amore clearly. Also fuel inlet 80 and air outlet 46 are shown in FIGURE 4for ease of comprehension of the control unit, although these ports areactually on the opposite side of the control unit from that viewed inFIGURE 4, as will be apparent from a consideration of FIGURES 2 and 3.

It will be apparent that many modifications and variations may beeffected without departing from the scope of the novel concepts of thepresent invention.

I claim as my invention:

1. In a turbo jet engine including a compressor section and anafterburner section having core and annulus fuel discharge means, valvemeans having core and an nulus valve ports controlling flow of fuel tosaid core and annulus fuel discharge means respectively, said valvemeans being angularly movable to progressively open the core valve portin a first range of angular positions and to progressively open saidannulus valve port in successive angular positions thereof beyond saidfirst range of angular positions, said valve means being axiallyshiftable to alter the fuel flow rate to at least one of said core andannulus fuel discharge means, and means responsive to compressordischarge pressure for controlling the axial position of said valvemeans.

2. In combination, a unitary assembly comprising a turbine driven fuelpump having a fuel inlet, a fuel outlet, an air inlet and an air outlet,a control housing having an air inlet and an air outlet, a fuel inletand a fuel outlet, means connecting said housing air outlet with saidpump air inlet, means for connecting said pump fuel outlet with saidhousing fuel inlet, fuel valve means in said housing for controllingfuel flow between said housing fuel inlet and said housing fuel outlet,said fuel valve means having first and second outlet valve portscontrolling flo-w of fuel therefrom, said fuel valve means beingangularly movable to progressively open the first valve port in a firstrange of angular positions of the valve member and to progressively openthe second valve port in successive angular positions thereof beyondsaid first range of angular positions, said valve means being shiftableaxially to vary the area of at least one of said valve ports inpredetermined angular positions of said valve means, air valve means insaid housing for controlling air flow between said housing air inlet andsaid housing air outlet,

and means responsive to the differential in pressure between saidcontrol housing fuel inlet and said housing fuel outlet controlling saidair valve means for maintaining a substantially constant fuel pressuredrop between said housing fuel inlet and said housing fuel outlet.

References Cited in the file of this patent UNITED STATES PATENTS2,447,423 Nies Aug. 17, 1948 2,674,847 Davies et al Apr. 13, 19542,688,842 Oestrich et al Sept. 14, 1954 2,724,239 Fox Nov. 22, 19552,739,442 Neal et al Mar. 27, 1956 2,742,755 Davies et al. Apr. 24, 19562,742,761 Mullen Apr. 24, 1956 2,770,945 Crim Nov. 20, 1956 2,774,215Mock et a1 Dec. 18, 1956 2,807,138 Torell Sept. 24, 1957 2,830,436 CoarApr. 15, 1958 2,836,957 Fox June 3, 1958 2,963,082 Binford et al Dec. 6,1960

